A partially reduced graphene oxide / glass fiber composite membrane and its preparation method and application

Abstract

The present invention relates to the technical field of gas separation membranes, and provides a partially reduced graphene oxide / glass fiber composite membrane, a preparation method thereof, and applications thereof. An ethanol dispersion of graphene oxide is filtered onto the surface of a glass fiber microporous filter membrane and dried to obtain a graphene oxide / glass fiber composite membrane; the graphene oxide / glass fiber composite membrane is heat-treated to obtain a partially reduced graphene oxide / glass fiber composite membrane. The present invention has high raw material utilization, a simple membrane preparation process, and uniform, orderly stacked membranes. The present invention utilizes a partial reduction strategy to fully utilize the synergistic effects of interlayer channel size screening and functional group interactions, significantly improving the H2 / CO2 selectivity of the partially reduced graphene oxide / glass fiber composite membrane. After application in gas separation testing, the H2 flux reached 730 GPU, and the H2 / CO2 separation selectivity reached as high as 4413.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation membranes, and in particular to a partially reduced graphene oxide / glass fiber composite membrane and a preparation method and application thereof. Background Art

[0002] Graphene oxide (GO), an oxide of graphene, is considered a promising material for small-molecule gas separation membranes due to its unique two-dimensional lamellar structure, excellent mechanical properties, superior chemical stability, and mature production process. For ultrathin GO membranes, the H2 / CO2 molecular sieving effect is primarily based on the pore size selection mechanism provided by the in-plane structural defects of the GO nanosheets. For example, Li et al. (Science, 2013, 342:95-98) fabricated ultrathin GO membranes by vacuum filtering monolayer GO nanosheets onto an anodic aluminum oxide (AAO) substrate. By leveraging the selective in-plane defects of GO, the resulting 9 nm thick ultrathin GO membrane exhibited an H2 / CO2 separation selectivity of 3400, with an H2 permeation flux of 341 gas permeation units (GPUs). However, the pre-purification of the monolayer GO nanosheets and the use of expensive inorganic porous substrates such as AAO make the preparation of ultrathin GO membranes complex and costly, making them unsuitable for industrial applications. This is a common problem faced by supported GO membranes in practical applications.

[0003] For layered GO membranes with stacked nanosheet structures, the H2 / CO2 gas separation mechanism mainly depends on the size screening effect of the two-dimensional channels between GO nanosheets and the interaction between CO2 molecules and oxygen-containing functional groups on the GO surface. However, the free space height between typical GO nanosheets (i.e., the interlayer channel size, h) is (ACS Nano, 2016, 10, 3398-3409.), larger than H2 and CO2 molecular dynamics diameter. Obviously, the excessively large original GO interlayer channel size is not conducive to the strict screening of H2 from the H2 / CO2 mixed gas. Even under the synergistic effect of the interaction between functional groups, the H2 / CO2 selectivity of the layered GO membrane prepared by the prior art can only reach a few hundred. For example, the H2 / CO2 selectivity of the spin-coated GO membrane with a uniform GO nanosheet stacking structure prepared by Chi et al. (Chemistry of Materials, 2016, 28, 2921-2927.) is only 240. Therefore, there is an urgent need to develop a simple and effective method to reduce the size of the GO interlayer channel while retaining the oxygen-containing functional groups as much as possible to improve the H2 / CO2 selectivity of the layered GO membrane.

[0004] In recent years, partially reduced GO membranes have gradually attracted attention in the field of molecular separation. For example, Qi et al. (Nature Communications, 2017, 8, 825.) prepared electrochemically reduced GO membranes on porous stainless steel hollow fibers (PSSSHF) by electrophoretic deposition (ED). Mildly reduced ED-GO@PSSSHF membrane (h: ) exhibited an ideal C2H4 / C3H8 selectivity (551), while the deeply reduced ED-GO layer (h: ) shows potential for hydrogen purification. This study provides a promising strategy for designing GO membranes for rigorous separation of H2 / CO2 mixtures, but electrophoretic deposition methods can only be applied to expensive conductive porous substrates. Therefore, designing a simple, effective, and low-cost method to prepare partially reduced GO membranes for efficient H2 / CO2 separation is of great significance for industrial processes such as industrial H2 purification and CO2 capture and utilization. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems in the prior art and provide a partially reduced graphene oxide / glass fiber composite membrane and a preparation method and application thereof.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a partially reduced graphene oxide / glass fiber composite membrane, comprising the following steps:

[0008] (1) filtering the ethanol dispersion of graphene oxide onto the surface of a glass fiber microporous filter membrane, and drying to obtain a graphene oxide / glass fiber composite membrane;

[0009] (2) The graphene oxide / glass fiber composite membrane is heat-treated to obtain the partially reduced graphene oxide / glass fiber composite membrane.

[0010] Preferably, the pore size of the glass fiber microporous filter membrane in step (1) is 0.20 to 0.24 μm.

[0011] Preferably, the concentration of the graphene oxide ethanol dispersion in step (1) is 0.02 to 0.04 mg / mL.

[0012] Preferably, in step (1), the diameter-to-volume ratio of the glass fiber microporous filter membrane to the ethanol dispersion of graphene oxide is 2.3-2.7 cm: 10-50 mL.

[0013] Preferably, the drying temperature in step (1) is 60 to 80° C., and the drying time is 12 to 24 hours.

[0014] Preferably, the atmosphere for the heat treatment in step (2) is one of air, nitrogen or vacuum.

[0015] Preferably, the temperature of the heat treatment in step (2) is 100-180°C.

[0016] Preferably, the heat treatment time in step (2) is 2 to 8 hours.

[0017] The present invention also provides a partially reduced graphene oxide / glass fiber composite membrane obtained by the preparation method.

[0018] The present invention also provides application of the partially reduced graphene oxide / glass fiber composite membrane in gas separation.

[0019] The beneficial effects of the present invention are:

[0020] (1) The present invention provides a method for preparing a partially reduced graphene oxide / glass fiber composite membrane, comprising filtering an ethanol dispersion of graphene oxide onto the surface of a glass fiber microporous filter membrane, and drying to obtain a graphene oxide / glass fiber composite membrane; heat-treating the graphene oxide / glass fiber composite membrane to obtain a partially reduced graphene oxide / glass fiber composite membrane; and using a conical vacuum filtration funnel in the filtration process to provide a centripetal force in the horizontal direction and a compressive force in the vertical direction. The synergistic effect of the external forces can suppress the negative effects of the repulsive interaction between graphene oxide nanosheets, thereby facilitating the preparation of a uniform and orderly stacked graphene oxide membrane.

[0021] (2) The partially reduced graphene oxide / glass fiber composite membrane provided by the present invention uses a commercial ultra-low-cost glass fiber microporous filter membrane as a porous substrate, which greatly reduces the cost of the substrate. In addition, the surface of the glass fiber is rich in oxygen-containing groups such as silanol, which can form hydrogen bonds and other interactions with the abundant oxygen-containing groups on the surface of graphene oxide, thereby improving the adhesion of the graphene oxide membrane to the substrate.

[0022] (3) The partially reduced graphene oxide / glass fiber composite membrane provided by the present invention directly uses an ethanol dispersion of commercial graphene oxide instead of pre-purifying single-layer graphene oxide nanosheets, thereby improving the utilization rate of raw materials and simplifying the membrane preparation process;

[0023] (4) The present invention adopts a partial reduction strategy to precisely reduce the size of the interlayer channels of graphene oxide nanosheets while retaining the oxygen-containing functional groups on the graphene oxide surface to the maximum extent, giving full play to the synergistic effect of interlayer channel size screening and functional group interaction, and greatly improving the H2 / CO2 selectivity of the partially reduced graphene oxide / glass fiber composite membrane; after application in gas separation tests, the H2 flux can reach 730GPU, and the H2 / CO2 separation selectivity is as high as 4413. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope characterization image of the GO / GF composite film prepared in Example 1;

[0025] Figure 2 X-ray diffraction patterns of the GO / GF composite film and the p-rGO / GF composite film prepared in Example 1;

[0026] Figure 3 This is a scanning electron microscope characterization image of the GO / GF composite film prepared in Example 2;

[0027] Figure 4 These are the X-ray diffraction patterns of the GO / GF composite film and the p-rGO / GF composite film prepared in Example 2. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a partially reduced graphene oxide / glass fiber composite membrane, comprising the following steps:

[0029] (1) filtering the ethanol dispersion of graphene oxide onto the surface of a glass fiber microporous filter membrane, and drying to obtain a graphene oxide / glass fiber composite membrane;

[0030] (2) The graphene oxide / glass fiber composite membrane is heat-treated to obtain the partially reduced graphene oxide / glass fiber composite membrane.

[0031] In the present invention, the glass fiber microporous filter membrane in step (1) is purchased and does not contain an adhesive.

[0032] In the present invention, the pore size of the glass fiber microporous filter membrane in step (1) is preferably 0.20 to 0.24 μm, more preferably 0.21 to 0.23 μm, and even more preferably 0.215 to 0.225 μm.

[0033] In the present invention, the ethanol dispersion of graphene oxide in step (1) is obtained by diluting a commercial graphene oxide dispersion.

[0034] In the present invention, the concentration of the commercial graphene oxide dispersion is preferably 1 to 2 mg / mL, more preferably 1.2 to 1.8 mg / mL, and more preferably 1.4 to 1.6 mg / mL.

[0035] In the present invention, the commercial graphene oxide dispersion is diluted to obtain an ethanol dispersion of graphene oxide containing single-layer graphene oxide nanosheets and large-diameter multi-layer graphene oxide nanosheets; the diameter of the graphene oxide nanosheets is preferably greater than or equal to 500 nm, more preferably greater than or equal to 505 nm, and more preferably greater than or equal to 510 nm.

[0036] In the present invention, the concentration of the graphene oxide ethanol dispersion in step (1) is preferably 0.02 to 0.04 mg / mL, more preferably 0.025 to 0.035 mg / mL, and more preferably 0.027 to 0.033 mg / mL.

[0037] In the present invention, the diameter-to-volume ratio of the glass fiber microporous filter membrane to the ethanol dispersion of graphene oxide in step (1) is preferably 2.3-2.7 cm:10-50 mL, more preferably 2.4-2.6 cm:20-40 mL, and more preferably 2.45-2.55 cm:25-35 mL.

[0038] In the present invention, the filtration in step (1) preferably uses a conical vacuum filtration funnel, the material of the conical vacuum filtration funnel is preferably polytetrafluoroethylene, and the material of the conical vacuum filtration funnel is preferably suitable for a 250 mL vacuum microporous membrane solvent filter.

[0039] In the present invention, the conical vacuum filtration funnel can provide centripetal force in the horizontal direction and compressive force in the vertical direction. The synergistic effect of the external forces can suppress the negative effects of the repulsive interactions between graphene oxide nanosheets, which is conducive to the preparation of uniform and orderly stacked graphene oxide films.

[0040] In the present invention, the drying temperature in step (1) is preferably 60-80°C, more preferably 65-75°C, and more preferably 68-73°C; the drying time is preferably 12-24h, more preferably 16-20h, and more preferably 17-19h.

[0041] In the present invention, the atmosphere for the heat treatment in step (2) is preferably one of air, nitrogen or vacuum.

[0042] In the present invention, the temperature of the heat treatment in step (2) is preferably 100-180°C, more preferably 120-160°C, and even more preferably 130-150°C.

[0043] In the present invention, the heat treatment time in step (2) is preferably 2 to 8 hours, more preferably 3 to 7 hours, and even more preferably 4 to 6 hours.

[0044] The present invention also provides a partially reduced graphene oxide / glass fiber composite membrane obtained by the preparation method.

[0045] In the present invention, the interlayer channel size of the partially reduced graphene oxide / glass fiber composite membrane is preferably More preferably More preferably

[0046] The present invention also provides application of the partially reduced graphene oxide / glass fiber composite membrane in gas separation.

[0047] In the present invention, the types of the gas are preferably H2 and CO2.

[0048] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] In the following examples, the glass fiber microporous filter membrane was purchased from Shanghai Xinya Purification Device Factory, and the commercial graphene oxide dispersion was purchased from Nanjing Xianfeng Nanomaterial Technology Co., Ltd.

[0050] Example 1

[0051] A glass fiber microporous filter membrane with a diameter of 2.5 cm, a pore size of 0.22 μm and no adhesive was used as an inorganic porous substrate, and a commercial graphene oxide dispersion with a concentration of 2 mg / mL was diluted to obtain a graphene oxide ethanol dispersion with a concentration of 0.03 mg / mL, containing graphene oxide nanosheets with a sheet diameter greater than or equal to 500 nm; a conical vacuum filtration funnel made of polytetrafluoroethylene was used to vacuum filter 10 mL of the graphene oxide ethanol dispersion onto the surface of the glass fiber microporous filter membrane, and after vacuum drying at 80°C for 12 h, a graphene oxide / glass fiber composite membrane (denoted as GO / GF composite membrane) was obtained; the graphene oxide / glass fiber composite membrane was heat treated at 160°C in an air atmosphere for 3 h to obtain a partially reduced graphene oxide / glass fiber composite membrane (denoted as p-rGO / GF composite membrane).

[0052] The GO / GF composite film prepared in this example was characterized by a scanning electron microscope at 5 μm, and a scanning electron microscope characterization image was obtained, as shown in FIG. Figure 1 As shown in the figure, it can be seen that the GO / GF composite film is evenly and orderly stacked.

[0053] The GO / GF composite membrane and p-rGO / GF composite membrane prepared in this embodiment were tested by X-ray diffractometer, and the obtained X-ray diffraction patterns were as follows: Figure 2 As shown; it can be calculated from the spectrum that the interlayer channel size of the p-rGO / GF composite membrane prepared in this embodiment is

[0054] The p-rGO / GF composite membrane prepared in this example was applied to gas separation tests, and the H2 flux of the composite membrane was obtained to be 730 GPU, and the H2 / CO2 separation selectivity was as high as 4413.

[0055] Example 2

[0056] A glass fiber microporous filter membrane with a diameter of 2.6 cm, a pore size of 0.23 μm and no adhesive was used as an inorganic porous substrate, and a commercial graphene oxide dispersion with a concentration of 1 mg / mL was diluted to obtain a graphene oxide ethanol dispersion with a concentration of 0.02 mg / mL, containing graphene oxide nanosheets with a sheet diameter greater than or equal to 505 nm; a conical vacuum filtration funnel made of polytetrafluoroethylene was used to vacuum filter 20 mL of the graphene oxide ethanol dispersion onto the surface of the glass fiber microporous filter membrane, and after vacuum drying at 60°C for 24 hours, a graphene oxide / glass fiber composite membrane (denoted as GO / GF composite membrane) was obtained; the graphene oxide / glass fiber composite membrane was heat treated at 140°C in an air atmosphere for 6 hours to obtain a partially reduced graphene oxide / glass fiber composite membrane (denoted as p-rGO / GF composite membrane).

[0057] The GO / GF composite membrane and p-rGO / GF composite membrane prepared in this example were tested using the same method as in Example 1, and scanning electron microscope characterization images of the GO / GF composite membrane were obtained. Figure 3 As shown; X-ray diffraction patterns of GO / GF composite film and p-rGO / GF composite film, as shown Figure 4 shown; from Figure 3 It can be seen that the GO / GF composite film is evenly and orderly stacked; Figure 4 It can be calculated that the interlayer channel size of the p-rGO / GF composite membrane prepared in this example is

[0058] The p-rGO / GF composite membrane prepared in this example was applied to gas separation tests, and the H2 flux of the composite membrane was obtained to be 692GPU, and the H2 / CO2 separation selectivity was as high as 2156.

[0059] Example 3

[0060] A glass fiber microporous filter membrane with a diameter of 2.4 cm, a pore size of 0.21 μm and no adhesive was used as an inorganic porous substrate, and a commercial graphene oxide dispersion with a concentration of 1.5 mg / mL was diluted to obtain a graphene oxide ethanol dispersion with a concentration of 0.04 mg / mL, containing graphene oxide nanosheets with a sheet diameter greater than or equal to 507 nm; using a conical vacuum filtration funnel made of polytetrafluoroethylene, 35 mL of the ethanol dispersion of graphene oxide was vacuum filtered onto the surface of the glass fiber microporous filter membrane, and after vacuum drying at 70°C for 18 hours, a graphene oxide / glass fiber composite membrane was obtained; the graphene oxide / glass fiber composite membrane was heat treated at 120°C in an air atmosphere for 7 hours to obtain a partially reduced graphene oxide / glass fiber composite membrane (denoted as p-rGO / GF composite membrane).

[0061] The p-rGO / GF composite membrane prepared in this example was applied to gas separation tests, and the H2 flux of the composite membrane was obtained to be 713GPU, and the H2 / CO2 separation selectivity was as high as 3762.

[0062] It can be seen from the above examples that the preparation method of the p-rGO / GF composite membrane provided by the present invention, while accurately reducing the size of the interlayer channels of graphene oxide nanosheets, retains the oxygen-containing functional groups on the surface of graphene oxide to the maximum extent, gives full play to the synergistic effect of interlayer channel size screening and functional group interaction, and greatly improves the H2 / CO2 selectivity of the partially reduced graphene oxide / glass fiber composite membrane; after the obtained p-rGO / GF composite membrane is applied to gas separation tests, the H2 flux can reach 730GPU, and the H2 / CO2 separation selectivity is as high as 4413.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a partially reduced graphene oxide / glass fiber composite membrane, characterized in that: It includes the following steps: (1) filtering the ethanol dispersion of graphene oxide onto the surface of a glass fiber microporous filter membrane, and drying to obtain a graphene oxide / glass fiber composite membrane; (2) heat-treating the graphene oxide / glass fiber composite membrane to obtain the partially reduced graphene oxide / glass fiber composite membrane; The filtration in step (1) uses a conical vacuum filtration funnel, the material of which is suitable for a 250 mL vacuum microporous membrane solvent filter; The temperature of the heat treatment in step (2) is 100-180° C.; the time of the heat treatment in step (2) is 2-8 hours; The interlayer channel size of the partially reduced graphene oxide / glass fiber composite membrane is 2.89-3.3 Å.

2. The preparation method according to claim 1, wherein The pore size of the glass fiber microporous filter membrane in step (1) is 0.20 to 0.24 μm.

3. The preparation method according to claim 1, wherein The concentration of the ethanol dispersion of graphene oxide in step (1) is 0.02 to 0.04 mg / mL.

4. The preparation method according to claim 3, wherein The diameter volume ratio of the glass fiber microporous filter membrane and the ethanol dispersion of graphene oxide in step (1) is 2.3-2.7 cm: 10-50 mL.

5. The preparation method according to claim 1, wherein The drying temperature in step (1) is 60 to 80° C., and the drying time is 12 to 24 hours.

6. The preparation method according to claim 5, wherein The atmosphere of the heat treatment in step (2) is one of air, nitrogen or vacuum.

7. The partially reduced graphene oxide / glass fiber composite membrane obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the partially reduced graphene oxide / glass fiber composite membrane according to claim 7 in gas separation.

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